Combined experimental and theoretical investigation of the premartensitic transition in Ni${}_2$MnGa

Abstract

Ultraviolet-photoemission (UPS) measurements and supporting specific-heat, thermal-expansion, resistivity and magnetic-moment measurements are reported for the magnetic shape-memory alloy Ni${}_2$MnGa over the temperature range $100K<T<250K$. All measurements detect clear signatures of the premartensitic transition ($T_{\mathrm{PM}}\sim 247K$) and the martensitic transition ($T_{\mathrm{M}}\sim 196K$). Temperature-dependent UPS shows a dramatic depletion of states (pseudogap) at $T_{\mathrm{PM}}$ located 0.3eV below the Fermi energy. First-principles electronic structure calculations show that the peak observed at 0.3eV in the UPS spectra for $T>T_{\mathrm{PM}}$ is due to the Ni-d minority-spin electrons. Below $T_{\mathrm{M}}$ this peak disappears, resulting in an enhanced density of states at energies around 0.8eV. This enhancement reflects Ni-d and Mn-d electronic contributions to the majority-spin density of states and is accompanied by significant reconstruction of the Fermi surface.

References in corpus (3)

• Observation of a strongly nested Fermi surface in the shape-memory alloy Ni[0.62]Al[0.38]
• Angle-resolved photoemission and first-principles electronic structure of single-crystalline $\alpha$-uranium (001)
• Electronic Instabilities in Shape-Memory Alloys

Cited by in corpus (1)

• Injective and non-injective realizations with symmetry